BibDocFile: register downloads with recid
BibDocFile: register downloads with recid

* Adds self.recid when calling `register_download()`.
  (closes #1831) (closes #1832)

Signed-off-by: Nikolaos Kasioumis <4c7685923ef4eda4c5f1e48e072c204c63d881cc@cern.ch>
Reviewed-by: Tibor Simko <c7116e45300b163846dc01f3ed02116e3f8ef7a5@cern.ch>

inveniosoftware/invenio,tiborsimko/invenio,tiborsimko/invenio,inveniosoftware/invenio